ML20085M584

NPDES Noncompliance Notification:Chronic Problem W/Ph Values Exceeding Limit of 9.0 at Outfalls 005,006A & 006B

ML20085M584
Person / Time
Site:	Summer
Issue date:	06/14/1990
From:	Summer S SOUTH CAROLINA ELECTRIC & GAS CO.
To:
References
RTR-NUREG-1437 AR, NUDOCS 9111110199
Download: ML20085M584 (3)

Text

- - - - _-__-__ _ _ _ .

ATTACHMENT 3 Suninary of Lagoon pH Problems I

I NPDES pH Limitation Com aliance Discharges 005,006A & dO6B There has been a chronic problem with pH values exceeding the NPDE5 Limit of 9 0 at outfalls 005, 006A and 006B. All of these discharge points involve lagoon treatment systems. When the renewed NPDES permit is issued, pH limits are expected to be restricted f urther, with an upper limit of 8 5.

These extreme pH values have been shown to be related to elgae growth in the lagoons.

The algae, though photosynthesis, change the carbon dioxide balance in the water which causes a change in pH, These pH changes are evident when adequate light and nutrients are available to the algae. Control of effluent pH at the affected outfalls can be approached in the f ollowing ways:

1. adjust the pH,

2. control or kill the algae,

3. reduce the nutrient load, and

4. reduce the light input.

Adjustment of the pH at the discharge has not been tried, since any addition of acid would require a SCDHEC construction permit. SCDHEC has informed us that suca a permit is not available to us since V. C. Summer Nuclear Station has an expired NPDES permit.

Construction permits would be considered when the renewed permit is issued We have attempted to control the algae in the lagoons by applying a chelated copper based algicide, K-teat Algicide application has resulted in limited success. There is reason -

to suspect that we are, through continuous use of this algicide, selecting for copper resistant types or strains of algae. It has been difficult to adequately treat the lagoons with algicide because of fluctuating flows through thelagoons and because of SCDHECimposed restrictions on copper concentrations in effluents to Monticello Reservoir The continued use of algicides is not suggested since the presence of algicides in the effluent will probably affect our ability to pass effluent toxicity testing which will be required in the renewed NPDES permit increased in plant chlorination levels have allowed very low levels of chlorine to be discharged into the alum sludge lagoon. The chlorine dissipates in the lagoon and is not measurable at the discharge (006A). This treatment appears to be effective in controlling the algae in the alum sludge lagoon Since the onset of pH problems appeared to coincide with the increased use of phosphate compounds for corrosion control, the use of these phosphate containing compounds has been reduced This reduction appean to have reduceci the magnitude of the problem, particularly in the sewage treatment lagoons (discharge 005) k kg 900614 1437 C pg

/

. s

. Pag 2 2 of 3 The plant surge basin (006B) was covered with black plastic to reduce the light input into the lagoon and thereby restrict photosynthesis. This appears to be very effective. This lagoon has had no algae related pH problems since it was covered. If this method is pursued f urther, a more permanent covering will have to be desinned One thing that has complicated evaluation of control methods is that different methods have been tried concurrently. For example, phosphate use was restricted during the same time period that chloie levels were increased The most promising options for control of algae related pH problems are listed below. l t

1. Install permanent structures over the ponds to decrease light input.

2. Use chlorination to control the algae in the ponds. l l

Adjust the pH at the outf alls by adding acid or carbon dioxide.  ;

3.

I Advantages and Disadvantages  !

of Options OPTION ADVANTAGE DISADVANTAGE i Light Exclusion a) low operating cost a) higher capital cost b) no manpower needed b) could complicate future modifications or for operation maintenance to lagoons such as liner inst allation, dike repair, or destudging c) may not be feasible for sewage lagoons Chlorination a) lower capital cost a) may not be feasible for sewage lagoons b) would not restrict any b) must be accompamed by dechlorination future modifications or at outfall maintenance c) safety considerations must be consider-ed if gaseous chlorine is used d) operating costs pH Adjustment a) lower capital cost a) safety considerations must be consider.

(acid) ed b) no restriction on future modification or b) operating costs maintenance pH Adjustment a) . low capital cost a) no pilot studies have been done to (CO2) determine degree of effectiveness b) no restriction on future modification or mainte- b) operating costs would be higher than nance light exclusion option

..m 1

• s Pcgo 3 of 3

]

It may be necessary to use a combination of the listed options, or use different options for different ponds. Also attention should be given to the use in the plant of any compounds that may contribute nutrient sources for the algae in the lagoons.

$ W- fYffo

5. E. Summer

)

l

]

.